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Started programming on a ZX spectrum in the 80's and have moved through Assembly, Turbo Pascal, C++, C#, Fortran. My main area of focus is engineering and scientific computing like numerical methods and 3D graphics. #SOreadytohelp


Jul
29
revised Is there a situation where $\left|d\vec{v} / dt\right|$ is non-zero while $d|\vec{v}| / dt$ is zero?
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Jul
29
comment Is there a situation where $\left|d\vec{v} / dt\right|$ is non-zero while $d|\vec{v}| / dt$ is zero?
Point taken. I will correct.
Jul
29
answered Is there a situation where $\left|d\vec{v} / dt\right|$ is non-zero while $d|\vec{v}| / dt$ is zero?
Jul
29
comment Is there a situation where $\left|d\vec{v} / dt\right|$ is non-zero while $d|\vec{v}| / dt$ is zero?
${\rm d} | \vec{v} | $ is confusing notation. Did you mean ${\rm d} \sqrt{ \vec{v}\cdot \vec{v}}$? Because I took it as $\sqrt{ {\rm d}\vec{v} \cdot {\rm d}\vec{v} }$.
Jul
29
comment Is there a situation where $\left|d\vec{v} / dt\right|$ is non-zero while $d|\vec{v}| / dt$ is zero?
Since $t$ is a scalar, $$\| \frac{{\rm d}\vec{v}}{{\rm d}t} \| = \frac{\| {\rm d}\vec{v}\|}{{\rm d}t} = \frac{{\rm d}\| \vec{v}\|}{{\rm d}t} $$
Jul
29
comment Virtual work (generalized forces) for rotation with Euler angles
Equation 7.2.31 in ocw.mit.edu/courses/mechanical-engineering/…
Jul
29
comment Virtual work (generalized forces) for rotation with Euler angles
Actually it comes from the power calculation. It is the unique value that maintains the powerflow through a joint. I also found it in slide 21 of diku.dk/OLD/undervisning/2005f/101/lecture11.pdf and slide 32 of homes.cs.washington.edu/~todorov/courses/amath533/…
Jul
29
answered Virtual work (generalized forces) for rotation with Euler angles
Jul
29
comment Virtual work (generalized forces) for rotation with Euler angles
Did you mean $\dot{\omega}=$ or ${\omega}=$ ? Angular velocity is $\omega=f(\dot{\phi},\ldots)$ and angular acceleration is $\dot{\omega}=f(\dot{\phi},\ddot{\phi},\ldots)$
Jul
28
answered Formula or relation for forcing spring movement over a certain time (as the image shows)
Jul
28
comment Can forces in N be thought of as a length?
Not like lengths, but like vectors.
Jul
28
revised Can forces in N be thought of as a length?
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Jul
27
comment Inelastic collision and conservation of linear and angular momentum
I agree, there is a momentum exchange between the two colliding bodies so the total momentum is maintained.
Jul
22
comment Trajectory of rolling billiard ball after collision with another billiard ball with same mass
\begin{pmatrix} x & y & z \end{pmatrix} => $\begin{pmatrix} x & y & z \end{pmatrix}$ See physics.stackexchange.com/help/notation
Jul
22
comment Is there a general rule for determining the direction of tension force?
Tension does not have a single direction. It is either tensile or compressive.
Jul
21
answered A lever arm-definition question
Jul
20
comment Observations of erratic rotation of asteroids
Actually no, any body would rotate about its center of mass in a predictable way in the absence of external forces.
Jul
20
answered rotational springs
Jul
20
comment rotational springs
A rotational spring still applies a linear force over distance (on the ends of the spring) to store/release work.
Jul
17
comment Applying impulse to velocity
Yes, $j$ is a scalar impulse value and $\bf n$ is a vector normal direction. Together they create a momentum exchange vector.